As large-size home televisions (TVs) have been steadily popular among consumers, the quality of displays in the TVs have become important factors for differentiating products from competitors. With the emergence of the ultra-high definition (UHD) TV age, other new techniques such as three-dimensional (3D) techniques, high frame rate techniques, and high dynamic range (HDR) techniques are also included in packaged UHD franchises. Although these various new techniques are provided in electronic devices, there is no technique for distinguishing a difference between UHD and HD by a user in a TV supporting new UHD.
The HDR technique has been popularized for photographing and camera technologies, but has not been used widely in video technologies due to incomplete standardization of the HDR technique.
For example, in spite of expansion of an HDR ecosystem through HDR-supporting displays and HDR-based content distribution, most contents are still generated by a standard dynamic range (SDR) technology due to the amount of legacy contents. In particular, since broadcasting stations implement the HDR technology in their ecosystems, broadcasting of HDR-based contents (e.g., live or pre-recorded contents) has been delayed. Fundamentally, a main issue of the HDR technology is how to match different peak luminances among contents and capabilities of various target devices, rather than how to generate the HDR-based contents.
In general, HDR-based contents may have large differences in peak luminance when compared to SDR-based contents, such that implementation for simple tone mapping algorithms is needed. Such tone mapping algorithms are algorithms of exclusive techniques depending on manufacturers, but most of them are based on simple linear tone mapping that increases a dynamic range of legacy contents according to capabilities of target devices.
FIG. 1 illustrates an example of a method for displaying contents in a conventional electronic device.
Referring to FIG. 1, an SDR-based content source 101 is linearly mapped according to a capability of a reproduction device 100 based on a peak luminance of the SDR-based content source 101. The reproduction device 100 displays the linearly mapped content.
Meanwhile, there are various conventional content techniques for displaying HDR-based contents. Current effort for the HDR technology involves standardization of the HDR-based contents and HDR-supporting display devices, but there was not much consideration of backwards capabilities and there is no standardized method for displaying SDR-based contents with maximal capabilities of HDR-supporting devices.
One of methods for providing HDR-based contents in conventional HDR-supporting devices is an inverse tone mapping process for converting SDR-based contents into HDR-based contents through unique additional metadata. The inverse tone mapping process is computationally intensive and is difficult to implement in case of absence of unique metadata from contents. In inverse mapping of SDR-based contents to HDR-based contents, the lack of unique metadata may output inconsistent results, which are unique to target device implementation and change not only luminances of the contents, but also colors of the contents, changing the intention of a contents generator.
FIG. 2 illustrates another example of a method for displaying contents in a conventional electronic device.
Referring to FIG. 2, SDR-based content 101 is converted into HDR-based content 103. Through inverse tone mapping between the SDR-based content 101 and the HDR-based content 103, metadata is obtained. Thereafter, the obtained inverse tone metadata is mapped to the SDR-based content 101, such that the mapped data is output to the reproduction device 100. Thus, the reproduction device 100 displays content to which the inverse tone metadata is mapped in the SDR-based content 101. That is, the reproduction device 100 displays the SDR-based content in which the content peak luminance is inversely tone-mapped according to the device capability.
In addition to the methods shown in FIGS. 1 and 2, there may be other conventional methods such as pixel-based color enhancement, or general changes for display setting, instead of changes in contents unique to titles. However, the conventional methods may be computationally intensive or may display contents (i.e., changed contents) that are different from a content source.
Therefore, a need exists for effectively displaying contents according to a capability of a reproduction device.